Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$60.28	3.687%	$62.5025	$62.50	$62.50	$62.50
Purchase #2	$243.58	10.214%	$268.4593	$268.46	$268.45	$268.50
Purchase #3	$13.41	6.626%	$14.2985	$14.30	$14.30	$14.30
Purchase #4	$184.76	11.113%	$205.2924	$205.29	$205.30	$205.30
Purchase #5	$189.52	3.638%	$196.4147	$196.41	$196.40	$196.40
Purchase #6	$48.90	11.713%	$54.6277	$54.63	$54.65	$54.60
Purchase #7	$164.57	10.703%	$182.1839	$182.18	$182.20	$182.20
7 purchase totals =	$905.02		$983.7790	$983.77	$983.80	$983.80